Image forming apparatus

Abstract

Provided is an image forming apparatus, which includes: a pressing lever and a pressing arm for pushing up a sheet stacking plate so that sheets stacked on the sheet stacking plate are brought into pressure contact with a sheet feeding portion; a lifter driving mechanism for driving the pressing lever and the pressing arm; and a setting mechanism disposed between the pressing lever and the pressing arm, and the lifter driving mechanism. The setting mechanism is capable of setting a pressure contact force for bringing the sheets stacked on the sheet stacking plate into pressure contact with the sheet feeding portion, to be appropriate for a size of the sheets to be stacked and an amount of the sheets to be stacked.

1. An image forming apparatus including a sheet feeding cassette which is provided to an apparatus main body and provided with a sheet stacking portion configured to stack sheets thereon, the sheet stacking portion being liftable for a cassette main body, and a sheet feeding portion configured to feed the sheets to be stacked, the image forming apparatus comprising:
 a lift member configured to push up the sheet stacking portion so that the sheets to be stacked are brought into pressure contact with the sheet feeding portion; 
 a plurality of springs coupled to the lift member, which are set to have one of the same spring constant and spring constants different from each other; 
 a driving mechanism configured to drive the lift member; and 
 a setting mechanism disposed between the lift member and the driving mechanism, and setting a pressure contact force for bringing the sheet to be stacked into pressure contact with the sheet feeding portion by selectively causing the plurality of springs to function with respect to the lift member according to a size of the sheets to be stacked. 
 
     
     
       2. An image forming apparatus according to  claim 1 , wherein the setting mechanism comprises:
 a plurality of racks arranged in parallel with one another as being engaged with one ends of the plurality of springs, the plurality of racks being movable in a direction of causing the plurality of springs to function; and 
 a pinion which is movable in a direction orthogonal to a moving direction of the plurality of racks, is moved to engage with a predetermined rack of the plurality of racks according to a size of the sheets to be stacked, and is rotated by the driving mechanism to move the predetermined rack. 
 
     
     
       3. An image forming apparatus according to  claim 1 , wherein the setting mechanism has a function of selectively causing the plurality of springs to function with respect to the lift member and a function of causing the plurality of springs to function simultaneously with respect to the lift member, according to a size of the sheets to be stacked. 
     
     
       4. An image forming apparatus according to  claim 1 , wherein:
 the sheet feeding cassette includes a regulating member for regulating a position of the sheets to be stacked, the regulating member being movable; and 
 the setting mechanism selects, from among the plurality of springs, a spring to function with respect to the lift member depending on the position regulated by the regulating member according to a size of the sheets to be stacked.